EVAL-AD1940EB View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-AD1940EB' PDF : 32 Pages View PDF
AD1940/AD1941
SERIAL DATA INPUT/OUTPUT PORTS
The AD1940/AD1941’s flexible serial data input and output
ports can be set to accept or transmit data in 2-channel formats
or in an 8- or 16-channel TDM stream. Data is processed in
twos complement, MSB first format. The left channel data field
always precedes the right channel data field in the 2-channel
streams. In the TDM modes, Slots 0 to 3 (8-channel TDM) or
Slots 0 to 7 (16-channel TDM) fall in the first half of the audio
frame, and Slots 4 to 7 (or Slots 8 to 15 in 16-channel TDM) are
in the second half of the frame. The serial modes are set in the
serial output and serial input control registers.
The two clock domains on the serial output ports can generate
two separate 8-channel TDM streams or one 16-channel TDM
stream. When in 16-channel TDM mode, the data is clocked by
LRCLK_OUT0 and BCLK_OUT0. The AD1940/AD1941 must
be in slave mode for 16-channel TDM mode, unless the data is
sampled at 48 kHz; the parts cannot generate a TDM bit clock
that is fast enough to support 96 kHz or 192 kHz. In 8-channel
TDM mode, the AD1940/AD1941 can be masters for 48 kHz
and 96 kHz data, but not for 192 kHz data. Table 36 displays the
modes in which the serial output port will function.
The input control register allows control of clock polarity and
data input modes. The valid data formats are I2S , left-justified,
right-justified (24-, 20-, 18-, or 16-bit), 8-channel, and
16-channel TDM. In all modes except for the right-justified
modes, the serial port accepts an arbitrary number of bits up to
a limit of 24. Extra bits do not cause an error, but they are trun-
cated internally. Proper operation of the right-justified modes
requires that there be exactly 64 BCLKs per audio frame. The
TDM data is input on SDATA_IN2 and SDATA_IN3 when in
2 × 8-channel TDM mode, and on SDATA_IN2 in 16-channel
TDM mode. The LRCLK in TDM mode can be input to the
AD1940/AD1941 as either a 50/50 duty cycle clock or as a bit-
wide pulse.
The output control registers give the user control of clock
polarities, clock frequencies, clock types, and data format. In all
modes except for the right-justified modes (MSB delayed by 8,
12, or 16), the serial port accepts an arbitrary number of bits up
to a limit of 24. Extra bits do not cause an error, but are
truncated internally. Proper operation of the right-justified
modes requires the LSB to align with the edge of the LRCLK.
The default settings of all serial port control registers
correspond to 2-channel I2S mode. LRCLK_OUT0 and
BCLK_OUT0 are clocks for Serial Output Ports 0 to 7, and
LRCLK_OUT1 and BCLK_OUT1 Clock Ports 8 to 15.
All registers default to being set as all 0s. All register settings
apply to both master and slave modes unless otherwise noted.
Table 37 shows the proper configurations for standard audio
data formats.
Table 36. Serial Output Port Master/Slave Mode Capabilities
fS
2-Channel Modes (I2S, Left-Justified, Right-Justified)
48 kHz
Master and slave
96 kHz
Master and slave
192 kHz
Master and slave
8-Channel TDM
Master and slave
Master and slave
Slave only
16-Channel TDM
Master and slave
Slave only
Slave only
Table 37. Data Format Configurations
Format
LRCLK Polarity LRCLK Type
I2S (Figure 23)
Frame begins on Clock
falling edge
Left-Justified
(Figure 24)
Frame begins on Clock
rising edge
Right-Justified
(Figure 25)
Frame begins on Clock
rising edge
TDM with Clock
(Figure 26)
Frame begins on Clock
falling edge
TDM with Pulse
(Figure 27)
Frame begins on Pulse
rising edge
BCLK Polarity
Data changes on falling edge
Data changes on falling edge
Data changes on falling edge
Data changes on falling edge
Data changes on falling edge
MSB Position
Delayed from LRCLK edge by one BCLK
Aligned with LRCLK edge
Delayed from LRCLK edge by 8, 12, or 16 BCLKs
Delayed from start of word clock by one BCLK
Delayed from start of word clock by one BCLK
Rev. A | Page 28 of 36
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